CN108666007A - Photovoltaic electrode silver paste - Google Patents

Abstract

The present invention discloses a kind of photovoltaic electrode silver plasm, and the electrocondution slurry is grouped as by the group of following parts by weight：75 ~ 92 parts of silver powder, 5 ~ 12 parts of organic solvent, 2 ~ 3 parts of organic carrier, 0.5 ~ 1 part of alkyl phenol polyoxyethylene ether, 0.8 ~ 5.3 part of microcrystalline glass powder；The grain size D50 of the microcrystalline glass powder is 0.3 2 μm；The microcrystalline glass powder is composed of the following components：10 ~ 50 parts of tellurium dioxide, 15 ~ 70 parts of lead oxide, 2 ~ 10 parts of zinc oxide, 1 ~ 15 part of molybdenum oxide, 5 ~ 20 parts of lithia, 0.4 ~ 2 part of alundum (Al2O3), 1 ~ 6 part of bismuth oxide, 1 ~ 4 part of calcium carbonate, 1 ~ 2 part of molybdenum chloride.Electrocondution slurry of the present invention effectively improves cell conversion efficiency, it may have high temperature viscosity is big, the big feature of surface tension, and slurry melten glass in sintering is not easy to flow, and keeps fine line style.

Description

Photovoltaic electrode silver paste

technical field

The invention relates to a photovoltaic electrode silver paste, which belongs to the technical field of solar cell functional materials.

Background technique

Photovoltaic cells, as an important branch of new clean energy, have achieved rapid development in recent years. Photovoltaic cell technology is also changing with each passing day. The entire industry chain is actively improving the conversion efficiency of photovoltaic cells and reducing costs through technological innovation, striving to achieve grid parity and replace traditional high pollution. energy.

Crystalline silicon photovoltaic cells are currently the most important type of photovoltaic cells, accounting for more than 90%. The principle of photoelectric conversion is: boron-doped P-type silicon and phosphorus-doped N-type silicon form a PN junction. The junction then absorbs photon energy to excite electron transitions, forming electron-hole pairs, thereby generating carriers.

The conductive metal paste is coated on the light-receiving surface (front) and the backlight surface (back) of the photovoltaic cell, and metal electrodes can be formed after sintering. The PN junction generates carriers that are exported through the metal electrodes to form a current. The metal electrode should form good ohmic contact with the silicon substrate, have lower ohmic contact resistance and volume resistance, reduce current loss, and improve solar cell conversion efficiency.

In order to achieve good ohmic contact and improve electrode conductivity, a lot of research has been done by technicians in the industry, in which glass plays an important role. For example, the glass needs to react with the anti-reflection layer (SiNx), and after the anti-reflection layer is etched away, it contacts with the silicon substrate. Moreover, the liquid glass can dissolve silver, and silver particles are precipitated in the silicon-based contact layer during cooling to reduce the ohmic contact resistance. Such as the principle of action of lead oxide and tellurium oxide studied by previous researchers. In addition, in previous studies, it was proposed to avoid glass devitrification, and it was believed that devitrification would cause adverse effects.

Contents of the invention

The invention provides a photovoltaic electrode silver paste. The photovoltaic electrode silver paste effectively improves battery conversion efficiency, and also has the characteristics of high viscosity at high temperature and high surface tension. When the paste is sintered, molten glass does not flow easily and maintains a fine line shape.

In order to achieve the above object, the technical solution adopted in the present invention is: a silver paste for photovoltaic electrodes, the conductive paste is composed of the following components by weight:

75~92 parts of silver powder,

5~12 parts of organic solvent,

2~3 parts of organic carrier,

Alkylphenol polyoxyethylene ether 0.5~1 part,

Metal glass-ceramic powder 0.8~5.3 parts;

The particle size D50 of the metal glass-ceramic powder is 0.3-2 μm;

The metal glass-ceramic powder is composed of the following components:

Tellurium dioxide 10~50 parts,

Lead oxide 15~70 parts,

Zinc oxide 2~10 parts,

Molybdenum oxide 1~15 parts,

Lithium oxide 5~20 parts,

Aluminum oxide 0.4~2 parts,

Bismuth oxide 1~6 parts,

Calcium carbonate 1~4 parts,

Molybdenum chloride 1~2 parts.

The further improved technical scheme in the above-mentioned technical scheme is as follows:

1. In the above scheme, the shape of the silver powder is spherical, polyhedral, short rod, dendritic or flake.

2. In the foregoing scheme, the organic solvent is at least one of terpineol, butyl carbitol, propylene glycol phenyl ether, propylene glycol methyl ether, dimethyl glutarate, and dimethyl succinate.

3. In the above scheme, the organic carrier is butyl carbitol acetate, ethyl cellulose, acrylate, oleic acid, polypropylene glycol, polyamide wax in a weight ratio of 75:7:6:4:3:5 mixed.

4. In the above scheme, the organic carrier is formed by heating, stirring and mixing at a temperature of 90 degrees.

Due to the use of the above-mentioned technical solutions, the present invention has the following advantages and effects compared with the prior art:

1. The photovoltaic electrode silver paste of the present invention contains 10 to 50 parts of tellurium dioxide, 5 to 70 parts of lead oxide, 2 to 10 parts of zinc oxide, 1 to 15 parts of molybdenum oxide and 5 to 20 parts of lithium oxide in its formula. "Metal glass-ceramic" can be precipitated during cooling. This metal glass-ceramic is applied to the silver paste of the front electrode of crystalline silicon photovoltaic cells. , The surface tension is large, the molten glass is not easy to flow when the slurry is sintered, and the fine line shape is maintained; secondly, 0.4~2 parts of aluminum oxide, 1~6 parts of bismuth oxide, and 1~2 parts of calcium carbonate are further added to the glass powder. 4 parts, to adjust the glass melting point and high temperature viscosity; again, its base tellurium dioxide 10~50 parts, lead oxide 5~70 parts, zinc oxide 2~10 parts, molybdenum oxide 1~15 parts, lithium oxide 5~20 parts system 1~2 parts of molybdenum chloride are further added to it as a co-solvent to promote the dissolution of glass and silver powder and lower the melting point.

2. The photovoltaic electrode silver paste of the present invention, its organic carrier adopts butyl carbitol acetate, ethyl cellulose, acrylate, oleic acid, polypropylene glycol, polyamide wax according to 75:7:6:4:3:5 The weight ratio is mixed, which not only helps to improve the wettability of the paste and the stainless steel screen plate, but also facilitates the uniform spreading of the paste during the printing process; moreover, it overcomes the problem that the silver powder and metal glass-ceramic powder in the conductive paste are easy to agglomerate and settle Defects, forming a uniform dispersion of silver powder and metal glass-ceramic powder.

Detailed ways

The present invention will be further described below in conjunction with embodiment:

Embodiment 1～4: a kind of photovoltaic electrode silver paste, described conductive paste is made up of the following components by weight:

Table 1

;

The above-mentioned organic carrier is formed by mixing butyl carbitol acetate, ethyl cellulose, acrylate, oleic acid, polypropylene glycol, and polyamide wax in a weight ratio of 75:7:6:4:3:5.

The above-mentioned organic carrier is formed by heating, stirring and mixing at a temperature of 90 degrees.

Note: embodiment 1 organic solvent is at least one in terpineol, butyl carbitol, propylene glycol phenyl ether, propylene glycol methyl ether, dimethyl glutarate, dimethyl succinate; embodiment 2 organic solvent It is a mixed solvent formed by butyl carbitol and propylene glycol phenyl ether; the organic solvent of embodiment 3 is propylene glycol phenyl ether; the organic solvent of embodiment 4 is a mixed solvent formed by terpineol and dimethyl glutarate.

The metal glass-ceramic powder is composed of the following components:

Table 2

Example 1 Example 2 Example 3 Example 4 Tellurium dioxide 10~50 parts 12 copies 30 copies 45 copies 24 copies Lead oxide 15~70 parts 45 copies 30 copies 60 copies 28 copies Zinc oxide 2~10 parts 8 servings 3 copies 5 copies 6 servings Molybdenum oxide 1~15 parts 4 parts 12 copies 6 servings 10 copies Lithium oxide 5~20 parts 9 servings 16 copies 6 servings 18 copies 0.4~2 parts of aluminum oxide 1.6 servings 0.6 parts 2 copies 1.2 parts Bismuth oxide 1~6 parts 2 copies 5 copies 3 copies 4 parts Calcium carbonate 1~4 parts 1.8 servings 3 copies 2 copies 1 copy Molybdenum chloride 1~2 parts 1.2 parts 1.8 servings 1.5 servings 1.4 parts

The metal glass-ceramic powder is obtained through the following steps:

Step 1. 10-50 parts of tellurium dioxide, 15-70 parts of lead oxide, 2-10 parts of zinc oxide, 1-15 parts of molybdenum oxide, 5-20 parts of lithium oxide, 0.4-2 parts of boric acid, chlorinated Mix 1~6 parts of molybdenum, 1~4 parts of silicon oxide, and 1~2 parts of barium carbonate, heat up to 900~1000°C under the mixture of _H2 and argon, keep it warm for 10~60 minutes to form glass liquid, and then put the glass liquid in Rapid cooling and forming on steel plate or stainless steel roller machine to obtain matrix glass;

Step 2. Heat the base glass at 200-400°C for 20-60 minutes in an oxygen-free atmosphere, and then cool it slowly at room temperature or with the furnace temperature to obtain metal glass-ceramics;

Step 3, then crush the metal glass-ceramic obtained in step 2 and then ball mill it with a planetary ball mill to obtain metal glass-ceramic powder.

The shape of the above-mentioned silver powder is spherical, polyhedral, short rod, dendritic or flake.

In the above step 1, the temperature was raised to 950° C., and the holding time was 30 minutes.

The heat preservation time in the above step 2 is 30 minutes.

The oxygen-free atmosphere in the above step 2 is vacuum, argon or nitrogen.

Solar cell device preparation:

A boron-doped P-type silicon substrate is selected as the semiconductor substrate, and the P-type silicon substrate is a 125*125mm or 156*156mm silicon wafer with a thickness of 180-250 μm or other typical sizes.

The first step is to corrode the pyramidal (single crystal) or uneven (polycrystalline) anti-reflection texture on one side of the silicon substrate with an alkaline solution, or use wet black silicon technology to make black silicon nano texture.

In the second step, an N-type diffusion layer is formed on the other side of the P-type silicon substrate to form a PN junction. The N-type diffusion layer can be a gas-phase thermal diffusion method using gaseous phosphorus oxychloride as a diffusion source, or a phosphorus ion implantation method, or Slurry coating containing phosphorus pentoxide, thermal diffusion method, etc.

The third step is to deposit a layer of 80nm thick SiNx anti-reflection layer on the textured side of the silicon substrate, or it can be other similar coatings with good anti-reflection effect.

The fourth step is to print or coat the Al electrode layer and the busbar silver electrode layer on the side of the P-type silicon substrate. In addition, SiNx or Al2O3 can also be used to form a passivation layer on the back of the battery as a back reflector to increase the long-wavelength light. absorb.

In the fifth step, the slurries of Examples 1 to 4 are formed on the anti-reflection film on the side of the N-type silicon substrate by screen printing, coating or inkjet printing, etc. to form vertical and horizontal main grids and fine grids, under a certain sintering temperature program , co-fired to form the electrode body. The recommended temperature sintering program is 250-350-450-550-600-700-800-900°C.

The electrical performance test of solar cells is performed under standard conditions (AM1.5, 1000W/m2, 25°C) using a solar analog electrical efficiency tester.

The contact resistance test method uses the commonly used TLM (Line Transmission Line Model) to test the contact resistance.

The test results are shown in Table 3:

table 3

When the above silver paste for photovoltaic electrodes is used, it can precipitate "metal glass-ceramic" when it is cooled. This metal glass-ceramic is applied to the front electrode silver paste of crystalline silicon photovoltaic cells, and has achieved better performance than conventional amorphous glass, effectively Improve battery conversion efficiency, also has the characteristics of high temperature viscosity and large surface tension, the molten glass is not easy to flow when the slurry is sintered, and maintains a fine line shape; secondly, it is based on 10-50 parts of tellurium dioxide, 5-70 parts of lead oxide, 2~10 parts of zinc oxide, 1~15 parts of molybdenum oxide, and 5~20 parts of lithium oxide are further added to the system with molybdenum chloride as a cosolvent to promote the dissolution of glass and silver powder and lower the melting point; again, the organic carrier is butyl Carbitol acetate, ethyl cellulose, acrylate, oleic acid, polypropylene glycol, and polyamide wax are mixed in a weight ratio of 75:7:6:4:3:5, which is not only beneficial to improve paste and stainless steel wire The wettability of the screen plate is conducive to the uniform spreading of the paste during the printing process; moreover, it overcomes the defect that the silver powder and metal glass-ceramic powder in the conductive paste are easy to agglomerate and settle, and forms a paste with uniform dispersion of silver powder and metal glass-ceramic powder .

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and the purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, and not to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (5)

1. a kind of photovoltaic electrode silver plasm, it is characterised in that：The electrocondution slurry is grouped as by the group of following parts by weight：

75 ~ 92 parts of silver powder,

5 ~ 12 parts of organic solvent,

2 ~ 3 parts of organic carrier,

0.5 ~ 1 part of alkyl phenol polyoxyethylene ether,

0.8 ~ 5.3 part of microcrystalline glass powder；

The grain size D50 of the microcrystalline glass powder is 0.3-2 μm；

The microcrystalline glass powder is composed of the following components：

10 ~ 50 parts of tellurium dioxide,

15 ~ 70 parts of lead oxide,

2 ~ 10 parts of zinc oxide,

1 ~ 15 part of molybdenum oxide,

5 ~ 20 parts of lithia,

0.4 ~ 2 part of alundum (Al2O3),

1 ~ 6 part of bismuth oxide,

1 ~ 4 part of calcium carbonate,

1 ~ 2 part of molybdenum chloride.

2. photovoltaic electrode silver plasm according to claim 1, it is characterised in that：The silver powder shape be ball-type, polyhedral, Stub shape, dendritic or piece type.

3. photovoltaic electrode silver plasm according to claim 1, it is characterised in that：The organic solvent is terpinol, butyl card It must at least one of alcohol, propylene glycol phenylate, propylene glycol monomethyl ether, dimethyl glutarate, dimethyl succinate.

4. photovoltaic electrode silver plasm according to claim 1, it is characterised in that：The organic carrier is butyl carbitol acetic acid Ester, ethyl cellulose, acrylate, oleic acid, polypropylene glycol, polyamide wax press 75：7：6：4：3：5 weight ratios mix.

5. photovoltaic electrode silver plasm according to claim 7, it is characterised in that：The organic carrier is under 90 degree of temperature conditions Heating stirring mixes.